Lumber drier



B. D. CURTIS.

LUMBER DRIER.

APPLICATION FILED MAR. 29, 1920- 1,407,786. r Patented Feb. 28, 1922.

4 SHEETSSHEET I.

ATTORNEYS.

B. 0. curms.

LUMBER DRIER.

APPLICATION FILED mmza, 1920. 1,407,786.

7 Patented Feb. 28, 1922.

4 SHEETS-SHEET 2- 1 ii II II IIIMIIIIIIII nIIm ATTORNEYS B. D. CURTIS. LUMBER DRIER.

APPLICATION FILED MAR-29,1920.

Patented Feb. 28, 1922.

4 SHEETSSHEET 3- 5 am, M W

'B. D. CURTIS.

LUMBER DRIER.

APPLICATION FILED MAR. 29. 1920.

Patented Feb. 28, 1922.

4 SHEETS-SHEET 4.

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Armmvmas.

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umrso STATES PATENT OFFICE.

BENJAMIN CURTIS, 0F PHILADELPHIA, PENNSYLVANIA.

LUMBER DRIER.

neomsc T 0 all 107M972 it may concern:

Be it known that I, BENJAMIN D. CURTIS, a citizen of the Llnited States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Lumber Driers, of which the following is a specification. p

My invention has reference, more particu larly, to a drier of the compartment type in which a quantity of lumber or other material is enclosed and subjected to heated air which is circulated therein so as to dry and season the lumber.

drying lumber, it has been found that the drying is more effectivelyaccomplished if the lumher is first subjected to a steaming treatment, as this opensthe pores of the lumber and facilitates thecemission of sap and moisture when the heatedair ispassed in contact with the lumber to dry'and season same, and my invention, inaddition to the drying faciiities, also has provision for affording the desired preliminary steam treatment. v

The principal objects of my invention are to provide an improved drying kiln adapted t afford effective recirculation of the air in the kiln to facilitate steaming or drying; to provide a drying kiln having animproved arrangement of selectively operable steamand drying devices which may be auto matieally controlled; toenforc'e recirculation by controlled cooling of walls of the drying kilnpto automatically regulate the exhaust of air from the drying kiln; to provide means fer indicating andrecording the effect of the steaming and drying operations on the lumber so as to enable the proper extent of each operation to be readily determined;

in general, to provide an improved dryu kiln of simple form and convenient to 1 ing of lumber may be expeditiously and thoroughly accomplishedj On the drawings, Fig. 1 is a horizontal, sectional view through the drying kiln and the adjoining operatorsroom, said view being talren substantiallyon the line 1-1 of Fig. 2; Fig.2, transverse, sectional View through the ,kiln taken on the line 22 of Fig. 1;

Fig. 3, a longitudinal, vertical, sectional view on the line, 3-3 of Fig. 1; Fig. 4, an enlarged,fragmentary view of the damper for controlling the admission of air to the air rate and use and provided withcontrol devices whereby the drying and season- Specification of Letters Patent. Patented Feb, 28, 1 922. Application filed March 29, 1920. Serial No. 369,770.

space in the are walls of the kiln; Fig. 5,

an enlarged, fragmentary, sectional View on h l -5 f F' 1 h h 1 L e me 0 01. 1g. s owing t e Va ve o1 tary, sectional view on the line 8-8 of Fig.

2 showing the automatic dampers in closed position; Fig. 9, a sectional view on the line 9 9 of Fig. 8 with the side wallgof the exhaust stack removed; Fig. 10, a detail "view showing the application of the recording device to the lumber in the drier; Fig. 11, an

enlarged face view of the recording device;

Fig. 12, a detail view showing the adjustable connection of the recording lever With the adjusting cable; Fig. 13, an enlarged,fragmentary, sectional viewon the line 13-13 of Fig. 3 showing the a Tangement of heatingcoils;, Fig. 14, a detail view of the top mounting of the adjustable hanger which supports the heating coils; and Fig. 15 a do tail of the bottom mounting thereof. 7

Referring to the drawings, the-reference numeral 1 indicates a rectangularfoundation or footing upon which the walls of the dry.-

ing compartment are built, the space en closed by the footing being filled in to any suitable height, as indicated at 2, excepting whereprovision is made as hereinafter. indicated for ducts and other openings. EX- tending lengthwise ofthe drying compartment between the side wallsthereof is a pit 3 with side walls twhich have rails 5 mounted on the top to support a car ortruck 6 upon which the lumber is piled or stacked and transported into and out of the drying compartment. intervals, extend over .the pit 3 and have their ends mounted in the sidewalls 4:, and may have a center rail 8 thereon to furnish additional support; for the truck 6.

The side walls of the drying compartment are composed of two separated sections 10 and 11, having an air space 12 therebetween, the inner section 11 being preferably somewhat thin so that the cooling effect of the air in the space 12 is communicated readily to the inner surface of the section 11. The wall sections 10 and 11 are connected together at the top so as to close the air space.

12 except at suitable intervals where stacks, or flues, project thereabove and afford ven- G'irders 7 placed at suitable tilation outlets for the air space 12. These fines are preferably covered by-caps 1a leaving side openings '15 thereunder, as shown.

Air is admitted to the air space 12 through an opening 16 at the end of each side Wall near the bottom thereof, each of which openings is regulated by a damper or door 17 sliding in upright ways 18'at each side of the opening and arranged in any suitable manner so that the door may be held in any position to which it is adjusted to regulate the admission of air to the air space 12. A grid 19 extends lengthwise of each wall 10-11 in the air space 12 at the level of or slightly above the top of the opening 16, the purpose of which is to afford even distribution of the air, entering through the opening 16, along the length of the wall 10ll for passage up through the air space 12 so that the interior of the wall sections 11 will be uniformly cooled. This grid 19 may be of any suitable construction, as for example, a grid plate mounted in and extending between the wall sections 10 and 11, or may.

consist of a course of brick suitably spaced apart and tying the wall sections 10 and 11 together. The wall sections 10 and 11 may, of course, be tied together at other points, if desired, so long as the means'employed does not interfere with the proper circulation of the air up through the air space 12;

The tracks 5 and 8 lead into the drying compartment at one end thereof and'this end of the drying compartment has a large opening 20 provided with one or more doors 21 which permit a loaded truck to be inserted in or removed from the compartment. These doors, of course, completely close the opening 2-Oand seal up that end of the compartment during the drying operation. The other end of the compartment is closed by a solid wall 80 with, of course, the necessary openings for air or other inlets therethrough, andhas an enclosure 81 at the outer side to afford an operators compartment 82, in which valves and other mechanism for controlling the operation of the drier are arranged for operation. Obviously doorways leading into the compartment 82 and from this compartment to the drying chamber may be provided to suit the convenience. A roof 83 entirely closes the top of the drier compartment, and, like the walls of the drier, may be of any desirable construction so long as it is heat resisting and does not readily'dissipate the heat in the drier compartment.

Extending along each side of the drier compartment adjacent to the side walls thereof and just below the floor line, is a large duct 8% which has a shield or cover plate 22 extending almost across the top thereof and with a wall 23 depending from the edge thereof almost to. thebottom of the duct '84, so as to leave a narrow space 24:

along the side wall of the drier through which draft circulation maytake place from the drying compartment to the duct 84. The

restriction of the passageway 24 serves to equalize the draft influence afforded by the draft duct, throughout the length of the side wall of the compartment and afford uniform circulation throughout the drying comparttion and have ventilators 27 or other suitably capped outlets at their upper ends.

Each stack 25 has a damper 28 mounted to slide therein in guides 29 and operableby a handle 30 projecting into the operators room 82 so that the draft or exhaust of air from the fines 25 may be manually controlled or entirely interrupted.

A pair of dampers 31 and 32 are pivoted at opposite sides of each flue 25 and each is substantially one half the transverse area of the flue so that they come together in hori- Zontal' position and close the flue, as shown in Fig. 8. These dampers or valves are an: tomatically controlled, or operated, by thermostatic devices arranged respectively at the exterior and interior of the drying compartment sothat the draft through the fiues25 is regulated automatically, in accordance with the temperature inside and outs-idethe drying compartment. The thermostatic devices which are indicated respectively at 3 4 and are the sameexcept as to the range of temperature within which they operate, and each comprises an expansible fluid container, (not illustrated in detail as such ele-. ments are well known) each of which is connected with a'bulb containing thermo-sensitive fluid. The bulb 34 which operates the element 34 islocated outside the drying compartment and connected by the tube 34: with the element 34- so that the latter contracts or expands in accordance with the temperature outside the drier, and the bulb 35 which operates'the element 35 is located inside the drying compartment and connected by the tube 35" with the element 35 so that the lat ter contractsand expands in accordance with the temperature inside the drier.

A lever 36 is pivotally mounted at one end adjacent the element 34 on a bracket 37'and connected with the moving part of said element by a stem or in other suitable manner so that the lever 36 is caused to swing on its pivot as the element 34 contracts or expands." The outer or free end of the lever 36 is con nected by the link 39 with a crank arm 40 on the pivot shaft 41 to which'the valve 32 is secured, said shaft being extended out through the side wall of the stack as indicated in Fig. 8 to enable the connection to be readily made. With this arrangement the lever 36 swings outwardly upon expansion of the element 34 and imparts an open' ing movementto thevalve 32, the range of operation of the element 34 being preferably from .to 100 F. so that the damper or valve 32 is closed at a temperature of 0 F. at the exterior ofthe drying compartment and open at 100 F.

The element 35 preferably has a range of operation Corresponding to the possible I drier. I

range of drying temperature in the drying compartment, as for example, from 100 F. to 200 FQ and is connected with the valve 31 so as to operate reversely to the valve 32,

that is, the valve 31 closes upon rise of tem-v perature inthe drier, whereas the valve 32 opensuponrise of temperature outside the The element 35 has a link and lever connection with'thearm 42 ofthe valve 31 similar to the connection of the element 34 with the arm of the valve32 and the corresponding parts are similarly designated on the drawing, The arm 42, however, extends in a direction from its shaft 43 opposite to that of the arm 40 so as to effect opposite movementv of the valves 31 and. 32by their thermostatic elements 34 and 35, and

the shaft 43 is extended laterallythrough the side wall of the stack 25 to facilitate malring the operating connection.-

In the bottom ofthe pin 3 is a pair of fines '47, each of which extends from end to end of the drying compartment and has a top 48 with apertures 49 arranged to ,dis-

tribute the supply of air from the fines, throughout the length ofthe drying com-.

partment. Each fine 47 opens out through the end wall 80 and the open end thereof is controlled by a valve 50 which may be ad:

justed and held in adjusted position in any convenient manner.

Each line 47 is connected with the duct 84. at thecorresponding side of the compart-y' number of spaced pipes 51 and the of each pipe51 in the duct 84 is All of the valves ment by a outer end controlled by a valve 52.

52 in each duct are connected to. a rod 53 mounted in sliding bearings and havinga handle 44 in the operators compartment 82 for adjusting the valves 52 to control'draft circulation through the pipes 51. i

The pit 3 steaming pipes and heating coils which extend from end any suitable manner from the I-beam girders"? and the latter being carried by and between the girders 7 and inverted channel beams 63 which extend across the pit 3 betweensthe walls4 near the bottom.

The steaming device comprises a pipe 55 p and trap 86*;

' controlled valve is provided to accommodate to end of the drying compartment, the former being suspended in.

running lengthwise of the pit 3 between the side wallswhich has branches 56' at the end connecting with return pipes57 arranged respectively adjacent the walls 4 and connected at their terminal ends by booster pipes 58* to the inlet end' of the center pipe 55. A

plurality of pipes 59, perforated their upper'surfaces, are connected at intervals along a the pipes 55' and 57 so as to'exhaust steam upwardly over a large area and are preferangular relation to the ably arranged in an pipes 55 and 57. These pipes 59 are loing provided with a downturned connecting portion 86 to prevent water of'cond'ensation' escaping through pipes 59. The pipes 55, 56 and 57 are sloped so as to drain tothe ends of the pipes 57 and discharge the water through a drainpipe 61 The inlet end ofthe pipe 55 cated between the girders and elevated above f the pipes 55 and 57, each'of said pipes 59 be-- the perforations of 7 the is connected with the steam main 87 through a manually operable valve 88 andatemperature controlled connected by the tube 90 with a bulb 91in the drying compartment for automatically regulating the supply of steamfby the temlperature in i the drying compartment. v

valve 89, which latter is c The heating device consists of p ite y inclined batteries of steam coils62 and opposite'sides of the pit 3,leach off which coils comprises a plurality of pipe lengths with 'f theends connected by. return bends so as to form a continuous steam duct. Theupper. 7

of the coils 65 and 62 is con-f length of each nected with'a cross pipe 92 which communi cates through the valve and temperature and the lower lengths of the'coils 62 and 65 are connected with acrosspipefl 93which ends thereof are preferably connected with 95 respectively so that each coil may be independently. removed for replacement or repairs. The coils 62 are mounted onhan'gers 96 which may be securetli at their upper and] lower ends respectively to the girders 7 and channel iron supports 63 by bolts or, clamps, I each of the coils 65"is preferably mounted for movement along the girders 7 and channeliron support 63so as to, permit access to be had to the various coils without, removing 3. This movable mount may be accomplished in same fromthe pit ingot-the coils 65 any suitable manner, as for example, by pro vidingth' hanger 97 upon which the coil 65. is mounted. with rollers 98 at the upper end engaging the lower and a roller 99 at the lower end engaging the top of the channeliron63. 1

For. determining ,the extent of thestcam;

ing and drying upon the lumber in the dry the pipesi92 and 93 through'unions 94 and.

or in any convenient mannen'iand flange of the girder 7' 8 9 with the steam main 8?,

p I y .165 leads 'to a trap 94. It will be observed that i each coil 62 or 65 independent and the lit ' through into contact with the lumber stacked 1 ing compartment 1 provide, preferably in the operators room 82, a recording instrument 66 which comprises an operating mechanismgsimilar to a recording temperature thermometer in the respect that it has any to the outer end of the cable 71 to maintain same. at a tension and the cable passes through asleeve 74 which may be adjustably secured thereto by the thumb screw 75. This sleeve .74 has a pivot pin 76 extending'therefrom through the lever 69 to permit the' necessary freedom of movement of thelever 69 as the-cable 71 is moved by the expansion and the contraction of the lumber. The dial 68' has a neutral line 77 marked thereon and the marking at one side of the neutral line by the stylus-serves to indicate the expansionof the lumber during the steaming operationfan'd the marking fat'the opposite side of the neutral line, the contraction dur ing the drying operation. a Y t i In using this drier, the lumber is stacked on the truck 6 in any 's'uitablemanner which will permit the steam and heatpenetrating to all parts of the stack and permit circulation of air therethrough, the floor ofthe truck being preferably constructed as an open; frame which permits the steam and heated air passing upwardly directly therethereon. This truck after loading is run into the drier compartment on the't'racks 5 and 7 'after'which the door 21 is closed to seal upthe drier compartment. WVhe'n the truck load of lumber is located in the, proper position the end of the cord or cable 71 is attachedto apiece of lumber on the pile near the top and the weight 73 at the end of the cable 1 holds the cable at a tension The stylus 69 is then adjusted at the neutral line77." l

The valves 28 in the stacks 25 are then closed and the valves 52 in the side draft chambers 84" opened and the doors 50 at the ends of the air passageways47 closed. '7 The valve 88 isopened so asto admit steam to the steampipes 59 which'is emitted through the apertures thereof and 'circulates up through'the stack of the lumber on the truck 6. The amount of steam admitted after the valve 88 is opened is automatically regulatedby the temperature in the drier compartment by' thefluidl in the bulb 91 y the automatic valves 31 which acts upon the automatic valve 89 to maintain a uniform temperature in the drier compartment. The valves 17 of the air inlets to the air space 10 of the side walls are opened during this operation so asto afford a cooling efiect on the inner sections of the ide walls and this cooling efiect" of the side wallsinduces a down draft along the side walls which causes the air, after it rises up through the stack of lumber, to circulate downwardly at each side of the compartment and enter the side draft openings 84 from whichit is drawn throughfthe pipes 51 to thepassageways fi at the bottom of the pit 3, from which it escapes through the apertures49 and circulates with the steam 1 from the jet pipes 59, up through the lum her-again. As the steaming operation con tinues the lumber becomes saturated and expands and the expansion of the stack of lumber is communicated through the cable 71 to the stylus 69 of the recording instrument which moves outwardly away from the neutral line 77 until the lumber is completely saturated, at whichtime the stylus 69 marks a line outside and parallel with the neutral line 77. When the stylus. marks such aline it is evident that the lumber is thoroughly saturatedand time for the steaming operation to be discontinued. The valve" 88 is 95 then closed and the valves-52 in'the side draft passageways likewise closed to prevent recirculation of the air, and the valve, 85'

opened so as to admit steam to the heating coils 62 and'65. The valves 28 in thestacks 25' are also opened and the "ventilation through the stacks then controlled entirely and 32. The" doors 50 controlling the supply ofjfresh air are opened so as to admit air into the pas-- sageways 47 which passes up through the perforated top'plates l9 and through'the heating coils 62 and 65 and then up through the stack of lumber on the truck 6." The valves 17 controlling admission of air to air space 10 in the side walls remains open during thedrying operation so as to cool the interior surfaces of the side walls sufliciently to enforce adown-draft along the side Wallsand the air thus passing downwardlyenters the side draft'passageways 8 1 through the air space 24. The circulation of air is regulated not only by the cooling of the side wallsof the drier but also by the automatic damper 31 and 32 which act to maintain a uniform circulation of air regardless of the temperature inside and outside the drier compartment. Assuming that the controlling element 34 is adapted to operate between'O F. and 100 'F., the valve 32 will be entirely open at an outside temperature of 100 and gradually close as the outside temperature decreases so that aid valve will be entirely closed at 0 F. Thus a low tem-- perature'outside' the drying compartment tions of outside temperature.

way so that the volume of air passing through the stack is diminished and the circulation or draft through the drier compartment kept uniform notwithstanding varia- The thermostatic element 35 serves the same purpose in connection with changes of temperature inside the drier compartment and is arranged, for example, to operate between the temperatures of 100 F. and 200 F. At 100 F. the valve 31 is entirely open and said valve gradually closes as the temperature in the drying compartment increases up to 200 at which point the valve 31 is closed. Thus a high degree of heat in the drier compartment which would tend to increase the circulation therefrom through the stacks 25 effects a suitable closing of the valve 31 so that the volume of air exhausted is constant, notwithstanding the variation in the draft.

From the foregoing it will be observed that if the temperature inside and outside the compartment is nearly 100 and there is, therefore, little difference in temperature to effect draft through the stacks 25, the valves 31 and 82 will be entirely open so as to permit free draft circulation to take place and as the difference in the inside and outside temperatures become greater and tends to enforce a greater degree of draft, through the stacks 25, the valves 31 and 32' are automatically adjusted so that the volume of air withdrawn from the drier compartment is substantially constant and the drying may, therefore, be effected at a uniform rate which will accomplish most, satisfactory results in drying the lumber. H

As the drying operation is carried on the natural moisture in the lumber and the moisture absorbed thereby in the Steaming operation, is gradually extracted by the circulating heated air and the stack of lumber, therefore, contracts, As the lumber thus contracts, the stylus 69 moves inwardly from ,the extreme outward position assumed at the time of steaming the lumber and crosses the neutral line 77 to the innerside thereof' When thestack of lumber becomes thoroughly dry the stylus 69 discontinues moving inwardly and marksa line on there'volvingrecord sheet 68 parallel with the neutral line 77 and thus indicates that the drying operation is completed. The truck load of lumber is then withdrawn from the drying compartment after which the steaming and drying operation is repeated on another truck load of lumber in the same manner.

The air spaces 10 in the side walls are intended to cool the inside surfaces of the side walls so that the air rising at the center of the drying compartment is drawn laterally toward each side and downalong the side walls to the side draft passageways 84;, and the cooling effect on the walls may be controlled by adjusting the valves 17 in accordance with the outside temperature to secure the desired rate of circulation in the drying compartment. a

While I have shown and described my invention in a particular form, I am aware that various changes and modifications may be made without departing from the'principles of my invention and I, therefore, do not propose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

1. In a drying kiln, the combination of an enclosure for the material to be dried, having heating means at the bottom forcreating air circulation upwardly through the enclosure, outlets from the enclosure at each side near the bottom thereof, and'means at opposite sides of the enclosure forenforc ing downward circulation of air within the pnclosure along each side wall to said outets.

2; In a drying kiln, the combination of an enclosure for the material to be dried, heating means at the bottom of'the enclosure, walls at each side of the enclosure,each comprising spaced sections with an airchamber therebetween, and having a draft outlet at the top of the air chamber and an air inlet thereto at the bottom, said air chambers being adapted to afford circulation through the walls for cooling the inner surfaces thereof, to enforce down draft in the enclosure adjacent each of the side walls, and valve-controlled ducts for conducting and distributing the downwardly directed air under the heating means.

In a drying kiln, the combination of an enclosure for the material to be dried having a draft passageway extending along each, side wall of the kiln near the bottom thereof,.restricted air inlet means extending tl'iroughout the length of the passageway to admit air thereto from theenclosure, and means for optionally exhausting the air from said draft passagewaysto the exterior of the enclosure, or returning same to the enclosure. v V p 4. In a drying kiln, the combination of an enclosure having the lateral walls thereof provided with air spaces, means for admitting air into the airspaces at the bottom of the wall and exhausting the air therefrom at the top so as to cool the interior surface of the wall and enforc'e downdraft in the entom, an air passageway undertheheating means leading from the exterior of the enclosure for admitting air into the enclosure below the heating means, a duct extending along each side wall adjacent the bottom ing the air to the exterior of the enclosure. 7. In a drying kiln, the combination of an, V enclosure for the material to be dried, having selectively operable steaming and heating means at the bottom thereof and exhaust ducts extending lengthwise thereof the side walls-adjacent the bottom thereof adapted to deliver air under the heating andsteaming means, outlets from the enclosure lead- 7 ing into the ducts near the bottom of the enclosure, and valves for selectively exhausting the air from the side ducts to the exterior of the enclosure or returning the air through the heating and steaming means into the enclosure.

8. In a drying kiln, the combination of an enclosure for the material to be'dried, having a side wall with an air space therein for cooling the inner surface of the wall so as to enforce circulation in the enclosure, means in the air space near the bottom thereof for effecting uniform distribution of air throughout the length of the wall, and an air inlet leading into the air space below i said means and having an adjustable door for controlling theadmission of air.

9; In a drying kiln, the combination-of an enclosure for the material to be dried,means for heating the material therein, a by-pass for conducting air to the heating means enclosure means for automatically controlling. they the air in pass for conducting air from the from the ieating means so as to recirculate the by-pass to the exterior of the enclosure and automatically adjustable means for regulating the draft outlet. v

10. .In a drying kiln, the combination of an enclosure for the material to be dried, means for heating the material therein, a byj to the heating means from a point in the enclosure at a distance from the heating means'so as to recirculate the air in the enclosure, a draft outlet from the by-pass leading to the exterior of the and thermostatically V operated draft outlet,

oint in the enclosure at adistance' the enclosure, a draft outlet from vl1. In a drying kiln, the combination of an enclosure for the material to be dried, means for heating the interior of the enclosure, a by-pass for conducting air to-the heating means from a point in t-heenclos'ure at a distance from the heating means so as to recirculate the air in the enclosure,-a draft outlet from the by-pass leading to the exterior of the enclosure and means automatically controlled by the temperature insideand outside the enclosure for regulating the draft outlet.

12. In a drying kiln, the combination of an enclosure for the material to be dried, means for heating the enclosure, a by-pass for conducting air to the heating means from a point in the enclosure at. a distance from the heating means so as to recirculate the air in the enclosure, a draft outlet from the by-pass leading to the exterior of the enclosure and means automatically regulated by the difference intemperatureinside and outside the enclosure for regulating the draft through the outlet.

13. In adrying kiln, the combination of an enclosure in which the materialis dried,

heating means for the enclosure,adraft outlet therefrom, a valve comprising two sections co-operab'le to control the draft -.through the outlet and means for independ ently controlling each valve section respectively, by the temperature inside the enclosure and the temperature outsidethe enclosure. L a

. 14. In a drying'kiln', the combination or an enclosure havingheating means adapted to create air circulation centrally up through the enclosure, side walls provided with cooling means for affording a down draft in the enclosure along the side walls, a draft passageway along the base of each side wall,

an outlet from each passageway to the exterior of the enclosure and thermostatically controlled means for regulating the exhaust throughfsaid outlets;

15,111 a drying kiln, the combination ofv an enclosure having means for heating the interior of the enclosure and thermostatically operated'meanscontrolled by the temperature in the enclosure-for regulating thefhea'tin'g means, and thermostatically "operated mean s'for controllingthe exhaustof air from theenclosure. i

16. In a drying kiln, the combination of an enclosure for the mat'eirialto be dried, independently operable heating and steaming means in the enclosure, and thermostatically operated means controlled by the temperature within the enclosure for regulating the operation of, the heating and steaming means, and thermostatically operated means for controlling the exhaust of air from the enclosure. @17. ."Infadrying kiln, the combination of an enclosure for the material to be dried,

and an indicator automatically operable by the expansion and contraction of the material which is being dried in the enclosure.

18. In a drying kiln, the combination of an enclosure for the material to be dried, means adapted to be connected with the material in the enclosure so as to be operable by the expansion and contraction of the material and an indicator at the exterior of the enclosure operated by said means.

19. In a drying kiln, the combination of an enclosure for the material to be dried, a recording dial adapted to have movement imparted thereto and a marker operated on said dial and adapted to be connected with the material in the enclosure so as to indicate on the dial the expansion or contraction of the material.

20. The improvement in the art of kiln drying lumber which consists in recirculating air through the lumber in the kiln chamber by withdrawing air from the chamber and returning the same thereto and at the same time mixing steam with the returned air and thereafter interrupting the recirculation of air and permanently withdrawing air from the chamber and supplying fresh air in place thereof.

21. A kiln for steaming and drying lumber, comprising an enclosure for the lumber, selectively operable heating and steaming means at the bottom of the enclosure for inducing a natural draft circulation of air upward through the lumber, exhaust ducts for withdrawing air from the enclosure adjacent the lower portion of its side wall, and having valve-controlled means for selectively delivering the air to the exterior of the enclosure or returning the same to the heating and steaming means for recirculation through the enclosure, and valvecontrolled means for admitting external air to the heating and steaming means,

22. A kiln for steaming and drying lumber, comprising an enclosure for the lumber, selectively operable heating and steaming means at the bottom of the enclosure, and a cooled side wall for inducing a naturaldraft upwardly through the lumber and downwardly along the side wall.

23. A kiln for steaming and drying lumber, comprising an enclosure for the lumber, selectively operable heating and steaming means at the bottom of the enclosure for inducing a natural draft circulation of air upward through the lumber, an exhaust stack, exhaust ducts for withdrawing the air from the enclosure adjacent the lower portion of said side Wall and having valve-controlled means for selectively delivering the air to said stack or returning the same to the enclosure.

24:. In a drying kiln, the combination of an enclosure for the material to be dried, having heating means at the bottom thereof, comprising laterally spaced inclined series of coils collectively joined to a single source of supply, said coils being arranged to evenly distribute the heatfrom the coils crosswise and longitudinally of the enclosure at low or high temperatures. i

25. In a drying kiln, the combination of an enclosure for the material to be dried, having steam-spraying means near the bottom thereof, comprising horizontal perforated pipes reversely extending from supply pipes and connected to .the latter so as to project therefrom angularly in the direction of the flow of steam in the supply pipes and extend crosswise and longitudinally of the enclosure, means for maintaining an even volume of steam at all the jets irrespective of their distance from the source of steam supply, and means for draining condensation from the spraying means.

BENJAMIN D. CURTIS. 

